Description:The computer ‘Administrator (built-in)’ preference item in the ‘Member_Server_Policy {AF5D1786-0EBF-4C78-BEAA-581F35735016}’ Group Policy object did not apply because it failed with error code ‘0x80070524 The specified account already exists.’ This error was suppressed.

After some initial troubleshooting I opted to modify the way the rename policy was setup by using a more traditional method for changing the administrator user account name

Open Group Policy Object Editor for the policy you want to use to rename the Administrator account, click Computer Configuration, click Windows Settings, click Security Settings, click Local Policies, and then click Security Options. Change the setting titled ‘Accounts: Rename administrator account.’